Friction Properties of Triazine Containing Hybrid Composites

Friction properties of triazine-containing hybrid composites

M. Mizerskia,b, I. Piwonskia, G. Celichowskia and S. Plazaa,*aDepartment of Chemical Technology and Environmental Protection, University of Lodz, Pomorska 163, 90-236 Lodz, Poland

bPharmaceutical and Clinical Research Center BIOFANA, Kutno, Poland

Received 20 September 2005; accepted 22 November 2005; published online 2 November 2006

This paper presents micro and nanofriction studies on thin silica/aminosilica-triazine hybrid composite coatings on silicon

substrate. The silica/aminosilica coatings were made on silicon using the dip-coating method and then modified by alkoxy- and

aryloxy-triazine derivatives. Formation of hybrid coatings permits a greater flexibility of their resulting properties. Microfriction

tests were carried out with a sliding ceramic ball (load range of 10–80 mN) on the composite flat surface, using a tribometer ball-on-

sample system. Sliding speed was 25 mm/min at room temperature. Nanofriction was measured using the Friction Force

Microscopy. It is shown that surface modification of silica/aminosilica layers by triazine derivatives, to form inorganic–organic

hybrid coatings, improves friction properties. All tested triazine derivatives, particularly long alkoxy- substituted s-triazines, cause a

decrease in the friction coefficients in microfriction tests, in comparison to a non-modified silica/aminosilica thin film. The same

effect was also observed for some tested triazine derivatives at nanofriction measurements.

KEY WORDS: friction-reducing, coatings, ceramic composite, surface modification, AFM, nanotribology

1. Introduction

Sol-gel processing is a method whereby small mole-cules can be converted into polymeric or ceramic mate-rials. Typically, one starts with molecules of the M(OR)4form, where R is an organic radical, such as CH3CH2–,or a halogen. The sol-gel method offers several advan-tages. For example, the nanocomposite so obtained isvery pure. The process occurs at a relatively low tem-perature that will not destroy the polymeric structure [1].

The hybrid coatings (thin films and composites) canbe formed in multiple steps, such as formation of a thinfilm of SiO2, followed by formation of one containing anaminosilane, in order to put amino groups on top of thefully formed SiO2 thin film. Holmes-Farley and Yanyo[2] observed that such bi-layer coatings gave betterstrength and corrosion protection, in comparison toone-layer coatings. Additionally, aminosilane-onlycoatings (thin films) neither provide inhibition on theirown, nor do they increase protection when applied ontop of a silica-only coating. Their experiments alsodemonstrate that the structure of these types of coatingssignificantly influenced the adhesion characteristics ofthe surface involved.

Cyanuric chloride and its derivatives have beenwidely studied in literature [3,4]. Such triazine deriva-tives are also useful as lubricating oil additives [5,6]. Ourrecent studies [7,8] confirmed that triazine derivatives

are good friction modifiers. Such coatings (also knownas functionally gradient coatings) [2] permit the prop-erties of different regions of a coating to be indepen-dently optimized for different properties. They mightinclude elastic modulus, adhesion promotion, index ofrefraction, friction coefficient, to name just a few. Thekey to the formation of triazine-containing hybridcomposites is controlling the reactivity of various tri-azine components in the modification reaction (lessor more reactivity, steric and electronic reasons). Alsothe choice of the organic group influences frictionalproperties of the resulting composite material.

The multiple procedures of the formation of multi-layer coatings would be significantly less desirable thanone in which the layer is formed in a single step, like inthe case of SiO2. The connection of inorganic silica withorganic parts (aminosilica) improves the surface adhe-sion. Unfortunately, the porosity of the surface increasesas well [2]. However, the amine group reacts easily withlots of chemicals (easy to substitute), the reaction withenvironmental vapor and carbon dioxide is the unde-sirable effect. In most cases, the surface modificationallows resolving all of these problems.

In this paper, the bi-layer composite materials, calledhybrid composites, are presented. The reinforcement ofsilica/aminosilica bi-layer material by triazines should bebetter than the one in which one-layer aminosilicacoating is modified. The methods of preparation andcharacterization of such composites form the secondpart of this paper.

*To whom correspondence should be addressed.

E-mail: [email protected]

1023-8883/06/1100-0119/0 � 2006 Springer Science+Business Media, Inc.

Tribology Letters, Vol. 24, No. 2, November 2006 (� 2006) 119

DOI: 10.1007/s11249-006-9043-6

2. Experimental

2.1. Materials

Commercial 3-aminopropyltriethoxysilane (APTS)and tetraethoxysilane (TEOS) were purchased fromFluka, and were used without further distillation. Tet-rahydrofurane (THF) was purchased from P.O.Ch.Gliwice, Poland, and was dried by the distillation in thepresence of Na/benzophenone and used directly afterdistillation. Toluene was also purchased from P.O.Ch.Gliwice, Poland, and azeotropically distillated beforemodification. Triazine modifiers are shown in table 1.They were prepared and tested by use of commontechniques [7,8].

2.2. Equipment

A Dip-Coating machine from NIMA� Technologieswas used to deposit the silica and aminosilica pre-con-densates onto the silicon surface, to obtain thin films ofbi-layer silica/aminosilica materials.

FT-IR Spectra were recorded with a BIORAD� FTS-175C System at 4 cm)1 resolution, using Harrick�

Refractor Reactor reflectance accessory with a MCTDetector, at room temperature. All spectra wereobtained in the 4000–650 cm)1 range, using RefractorReactor accessory with MCT detector. Pure siliconwafer was used as a background sample.

The samples were frictionally tested on the recipro-cating ball-on-flat machine, constructed in the Depart-ment of Chemical Technology and EnvironmentalProtection, University of Lodz, Poland. The deviceconsists of the control and the testing blocks. The con-trol block is a computer-based unit, with four channelsof data acquisition (total sampling rate up to 100 kHz)and computerized motor controllers for motion in the xand y-directions, and a system of normal load applica-tion. The Microtribometer can provide linear motionwith a speed ranging from 2 to 2000 lm/s. Normal load,which can be applied during frictional tests, covers themili-Newton scale (1–1000 mN). Standard frictionalpairs are a flat surface covered by a thin film and aceramic or metallic ball of 1–5 mm diameter as acounterbody.

The AFM/LFM topography of sample surfaces andnanofriction measurements were performed with aNT-MDT Solver system, using the Si/SiO2 tips.

2.3. Preparation of silica/aminosilica thin films (TA)

In the first step, a thin film of silica on silicon wasprepared as follows: 2.07 g (0.1151 mol) water withhydrochloric acid (0.1 M HCl solution as catalyst) wasadded to 6 g (0.0288 mol) TEOS. After the hydrolysis ofTEOS and the condensation processes, a clear silicaprecondensate was obtained, that was next diluted withethanol (99.8% pure alcohol) in the ratios of 1:1 (w/w).Then, the solution of precondensate was filtered anddeposited on a silicon wafer using the dip-coater at thesliding velocity of 25 mm/min, and next, the layer wasdried and heated (100 �C, 2 h). In the next step, theaminosilica precondensate was prepared as follows:1.46 g (0.0813 mol) water with hydrochloric acid (0.1 MHCl solution as catalyst) was mixed with 6 g(0.0271 mol) of 3-APTS. After 24 h, with the clearprecondensate, the procedure was repeated like in thesilica thin film method. The product, called TA (silica/aminosilica), was preheated before further modification(80 �C, 2 h), to decompose hydrocarbonate ammonium,which is formed in reaction of amine groups with CO2 inthe presence of the ambient humidity [9].

The thickness of the ‘‘active’’ aminosilica layer in TAmaterials had been determined before, by combiningSEM and FT-IR measurements [8]. The thickness ofprepared aminosilica was �600 nm. The scheme of theprocess of preparation of the TA bi-layer coating isshown in figure 1.

2.4. Preparation of hybrid composites

The TA materials were modified by triazine deriva-tives, according to the scheme of reactions shown infigure 2. Abbreviations of hybrid composites used in thispaper are presented in table 2. The general procedure ofsynthesis of these materials was as follows. The TAmaterial on silicon pre-heated at 80 �C (2 h) was putinto the 1% (0.2 g) THF (or toluene) solution of thetriazine modifier in a round flask. After that, the molar

Table 1.

Triazine surface modifiers.

R Groups Abbreviation Name (-1,3,5-triazine)

N

NN

OR

OR

Cl or RO

CH3 CDMT 2-chloro-4,6-dimetoxy-

(CH2)7CH3 C8T 2-chloro-4,6-dioctyloxy-

CH2-Ar BzT 2-chloro-4,6-dibenzyloxy-

CH2CF3 CF3T 2-chloro-4,6-bis (2¢,2¢,2¢-trifluoro)ethoxy-CH2(CF2)7CF3 FCDMT 2-chloro-4,6-bis- (1H,1H-perfluorononyl-1-oxy)-

Ar TPhT 2,4,6-trifenoxy-

Ar-F5 PhF5 2,4,6-tris(pentafluorofenoxy)-

120 M. Mizerski et al./Friction properties of triazine composites

equivalent of DIPEA was added (depending on themolecular weight of the triazine derivative). The wholesample was then refluxed with the solvent (bp temper-ature). After 24 h, the modification process was finished.The sample of TA-modified composites was washedwith some portion of solvent, and ultrasonificated for10 min. Finally, the prepared sample was refluxed withthe adequate solvent, using a Soxhlett extractor, for6–12 h. The scheme of the process of preparation of theTA-m composites (hybrid composites – TA-modified) isshown in figure 2. The increase of the hydrophobicityafter the modification of aminosilica surface allowed toresolve the problem of the spontaneous reaction ofamine groups with the environmental vapor and CO2.

The reaction process was controlled by 4-(4¢-nitrob-enzyl) pyridine colorful test [10]. The mechanism of thiscolorful reaction is presented below in figure 3.

2.5. Microtribological measurements (Microfriction)

The friction coefficients were determined in a ball-flat disk configuration of sample frictional contact.The ball was made of zirconia, stabilized by yttriumoxide (ZrO2 97%, Y2O3 3%), and had a 3 mmdiameter. The reciprocating movement was used, atthe speed of 420 lm/s, on 20 mm distances. The loadapplied was in the range from 10 to 80 mN. All thefriction tests were conducted at room temperature.The friction coefficient was calculated from an averagevalue of full distance, excluding start and end points,where the speed is not stable.

2.6. Nanotribological measurements (Nanofriction)

The AFM/LFM measurements were carried out inthe contact mode, with direct recording of topographyand friction images. All of the AFM/LFM measure-ments were of a relative character. The method ofdetermination the relative friction coefficient is shown infigure 4.

Si

OC2H5

OC2H5

OC2H5

H5C2OOH2

C2H5OH

Si

OH

OHOH

OHO

Si

OO

O

*nSi

OC2H5

OC2H5

OC2H5

H5C2O

hydrolysis

+ 4

- 4

condensation

4

TEOS thin film (SILICA)

Si

OC2H5

OC2H5

OC2H5NH2

OH2

C2H5OH

Si

OH

OHOH

NH2

Si

OC2H5

OC2H5

OC2H5NH2

NH2 Si

OO

O

*n

APS thin film (AMINOSILICA)

hydrolysis

+ 3

- 3

condensation

3

Silicon Wafer

Aminosilica APSSilica TEOS1.

2.

TA material

1

2

Figure 1. Preparation of the TA material.

NN

NRO or Cl

O-R

O-R N(iPr)2(Et) , THF or Toluene

N

NN

NH

O-R

O-RNH2

THF or Toluene12-24h +

- HN+(iPr)2(Et)Cl-

TA material triazine modifierTA-m Anisotropic composites(RO- FUNCTIONALLYGRADIENT GROUP)

1.

2. Soxhlett reflux

Figure 2. General procedure of synthesis of TA-modified triazine hybrid composites.

Table 2.

Abbreviations used for the composite materials.

No. Composite TA-m

abbreviations

Triazine modifiers

abbreviations

1 TA-CDMT CDMT

2 TA-C8T C8T

3 TA-BzT BzT

4 TA-TPhT TPhT

5 TA-CF3T CF3T

6 TA-FCDMT FCDMT

7 TA-PhF5T PhF5T

M. Mizerski et al./Friction properties of triazine composites 121

3. Results and discussion

3.1. FTIR Analysis of hybrid composites

The analysis of silica/aminosilica (TA) and hybridcomposites was performed to confirm their structures.Figure 5 shows typical FTIR spectra (TA-CF3T hybrid)of the TA surface, modified by 2-chloro)4,6-bis(2¢,2¢,2¢-trifluoroethoxy)-1,3,5-triazine (CF3T), including thespectrum of unmodified TA, for comparison. TheFT-IR spectra of remaining hybrid materials are sum-marized below as the observed frequencies of theabsorption bands with qualitative intensities and theircorresponding groups.

TA (silica/aminosilica): (IR, cm)1) 3368, 3286 (w,NH); 2929, 2863 (s, C–H); 1589 (m, NH); 1391 (w, C–H,–CH2Si); 1219, 1148, 1039 (vs, Si–O–Si, Si–O). Theremaining parts of the spectra were confirmed apartfrom Si–O bonds and C–H (str – aminopropyl chainthat existed on every spectrum.

TA-CDMT: 3283 (m, NH-triazine); 1618 (m, def,NH-triazine); 1584 (s, C=N triazine); 1535, 1505, 1419(s, s, m, triazine ring); 806 (s, def, triazine ring).

TA-TPhT: 3277 (m, NH-triazine): 3058, 3030 (m, C–H,C6H5O–); 1663 (s, C=C, C6H5O–); 1603 (s, combined,NH-triazine def, C=N triazine); 1517, 1495, 1451, 1347(s, s, s, s triazine ring); 1410 (m, combined triazine andbenzene ring); 803 (s, def, triazine ring).

TA-C8T: 3288 (m, NH-triazine); 1618 (s, def,NH-triazine); 1578 (s, C=N triazine); 1533, 1477, 1433(s, s, s, triazine ring); 1406 (s, combined triazine ring,CH [C8H17O–]); 807 (s, def, triazine ring).

TA-BzT: 3245 (n, NH-triazine); 3094, 3020, 3001 (m,CH, –CH2–C6H5); 1612 (s, combined, C=N triazine,C=C benzyl); 1511, 1410, 1337 (s, s, s, triazine ring);1466 (s, combined triazine ring, benzyl C=C); 807(s, def, triazine ring).

TA-CF3T: 3273 (m, NH-triazine); 1616 (m, def, NH-triazine); 1554, 1472, 1333 (s, s, s, triazine ring); 1410(s, combined C–F [CF3CH2–] and triazine ring); 1397(s, C–F CF3CH2–); 803 (s, def, triazine ring) – presentedas an example in figure 5.

TA-FCDMT: 3292 (m, NH-triazine); 1610 (m, def,NH-triazine); 1589 (s, C=N triazine); 1544, 1470 (s, s,triazine ring); 1413 (s, combined C–F [C8F17CH2–] andtriazine ring); 1350 (s, C–F [C8F17CH2–]); 807 (s, def,triazine ring).

TA-PhF5T: 3240 (m, NH-triazine); 1627 (s, combinedNH-triazine, def and C=C [C6F5]); 1595 (s, C=N tri-azine); 1578, 1529, 1340 (s, s, s, triazine ring); 1385, 1312(s, m, C–F [C6F5O–]); 825 (s, def, triazine ring).

In our recent studies [7,8], the Secondary Ion MassSpectrometry (SIMS) was also used as an alternativemethod for confirmation of molecules structures. Forexample, table 3 contains data for aminosilica hybridAPS-CF3T (aminosilica thin film, on a silicon-modified

N

NN

OR,OAr,Cl

OR,OAr,Cl

N+

N+

O

OCH2 Cl

N

NN

OR,OAr,Cl

OR,OAr,Cl

NN+

O

OCH

N+

O

ONCH2

N

NN

OR,OAr,Cl

OR,OAr,Cl

Cl+

4NBP

+ 4NBP- 4NBP*HCl

Figure 3. General procedure of 4NBP-test.

y = 0,1444x +1,8402

0

0,5

1

1,5

2

2,5

3

3,5

-1 0 4

Friction Force [a.u.]

Nor

mal

For

ce [n

A]

TA-PhF5T

y = ax + b a - Relative Friction Coefficient

1 2 3 5 6 7 8

Figure 4. Determination of the relative friction coefficient for the

TA-PhF5T composite.

Figure 5. IR Spectra of the TA material (dotted) and TA-CF3T

hybrid composites (black).


fluorinated triazine derivative CF3T). Both mono-(previously investigated) and bi-layered materials (inthis work) were modified in the same way. In conse-quence, they had a similar chemical constitution of themodified surfaces. In addition, the results of the SIMSanalysis would not differ much. Therefore it was notadvisable to analyze the bi-layered hybrids. The FTIRand the ToF-SIMS analysis provides a clear evidence ofchemical reactions between amine group of TA andtriazine derivatives on the surface.

3.2. Microfrictional properties

The results of microfrictional measurements of sevenhybrid composites are presented in figures 6 and 7. Theyshow that all of them have lower values of frictioncoefficients, in comparison to the TA material. Theaminosilica forms low-hardness coatings (soft). It allowsresolving this problem by surface modification. The

coating hardness should grow up undoubtedly. It issupposed to be true, because the differences between thefrictional properties of modified and non-modifiedmaterials are much more significant.

This reinforcing capability could be also attributedto the character of the substitution in the triazine ring.The results clearly show the differences in frictionalperformance of composite materials.

The increasing length of the carbon chain fromshort (TA-CDMT, TA-CF3T) to long (TA-C8T, TA-FCDMT), results in the significant decrease of frictioncoefficient values. The reason for such behavior mayarise from the reinforcement of the condensed layer bycohesion forces, formed between long carbon chains –(CH2)7–CH3 and CH2–(CF2)7–CF3, as in the exampleof TA-C8T, shown in figure 8(a). TA-C8T andTA-FCDMT are most effective in the reduction offriction, among all prepared composites. Their values ofthe friction coefficient, in the whole range of loads, are0.11 and 0.14, respectively. The reinforcing efficiency is

Table 3.

Results the ToF-SIMS analysis of aminosilica coating (APS) modified CF3T triazine [2-chloro-4,6-bis(2¢,2¢,2¢-trifluoroethoxy)-1,3,5-triazine].

Ion fragment Ion type m/z APS (aminosilica coating) lot of counts APS-CF3T (aminosilica hybrid) lot of

counts

Positive mode Negative mode Positive mode Negative mode

CH2NH2 P 30.05 7979 – 3370 –

C3N3H3 P 81.03 – – 14 806 –

C3N3H2 P 67.02 – – 30 676 –

CF3 P 69.01 – – 5200 –

CF P 31.01 – – 4800 –

CF3CH2 P 83.02 – – 3600 –

CH2F P 33.03 – – 6400 21 600

CH2O N 30.02 – 2050 28 394 7340

F N 19.00 – 60 484 – 107 400

CN N 26.02 – 73 038 – 83 286

HCN N 27.03 – 807 – 6200

CNO N 42.02 – 2200 – 110 154

C2N2O N 68.00 – – – 4800

H2C2N2O N 70.02 – – – 17 660

0,00

0,05

0,10

0,15

0,20

0,25

0,30

0,35

0,0

10,0

20,0

30,0

40,0

50,0

60,0

70,0

80,0

90,0

Load [mN]

Fric

tion

coef

ficie

nt µ

TA-CDMT TA-TPhT TA-C8TTA-BzT TA

Figure 6. The effect of load on the friction coefficient for non-

fluorinated composites in the micro-scale.

0,00

0,05

0,10

0,15

0,20

0,25

0,30

0,35

0,0

10,0

2,00

30,0

40,0

50,0

60,0

70,0

80,0

90,0

Load [mN]

Fric

tion

coef

ficie

nt µ

TA TA-CF3T

TA-FCDMT TA-PhF5T

Figure 7. The effect of load on the friction coefficient for fluorinated

composites in the micro-scale.


higher for TA-C8T, replacing the hydrogen atoms inthe hydrocarbon chain (TA-C8T) with the fluorineones (TA-FCDMT) decreases the antifriction action.The friction performances of short-chain hybrids(TA-CDMT, TA-CF3T) are nearly the same.

The composite materials including phenyl groups givehigher values of friction coefficient than other compos-ites. It can be explained by the steric effect of (TA-TPhTand TA-BzT) molecules, which decreases the antifric-tional properties. The steric compression causes that notall of the amine groups participate in the reaction ofmodification, as it is presented in figure 8(b). This maysuggest that higher values of friction coefficient shouldhave been observed for fluorinated aromatic ring likePhF5T (nanocomposite TA-PhF5T) (figure 8(c)).

In the microtribological tests, the friction coefficientvalues for TA-PhF5T composites are nearly the same asfor non-substituted aromatic composites TA-TPhT andTA-BzT. Probably, there exists a combination of at leasttwo opposite effects. On the one hand, the steric effectcauses the rise of friction coefficient. On the other hand,the fluorine electron withdrawing substituents are wellknown for their influence on reduction of friction. Thenet result of these competitive effects is that the frictioncoefficient of TA-PhF5 is not lower. Generally, alkoxy-triazines are better surface modifiers than aryloxy-triazines in microfriction conditions. The order ofimprovement in the antifrictional activity in the micro-scale is:

C8T > FCDMT > CDMT ¼ CF3T > BzT

¼ TPhT ¼ PhF5T:

Although this paper does not present results of wearresistance tests of triazine-containing hybrid composites,it is supposed that the modification of aminosilica sur-face improves antiwear performance in comparison tostarting bi-layer silica/aminosilica coating. Long carbonchain- and aromatic-containing (especially fully fluori-nated) materials (i.e. composites, lubricants), are well-known and used in tribology. Mostly, they causeimprovement of frictional and antiwear performance ofmaterials. It is believed that the effect of such groups

into aminosilica surface should be nearly the sameamong all of testing hybrids, TA-C8T, TA-FCDMT,TA-PhF5T are expected to have the best wear resistancecharacteristic.

3.3. AFM studies

The topographies of surfaces before and after themodification are shown in figure 9. It can be clearly seenthat modification of the surface occurs. The results ofnanofriction tests are given in figures 10 and 11.

As noted before, the presented values of frictioncoefficients obtained in nanofriction conditions are inarbitrary units, allowing us only to derive tendencies infriction coefficients and to compare the investigatedmaterials. A higher antifriction efficiency was observedfor the carbon-chain substituted nanocomposites:TA-C8T and TA-CDMT, and fully substituted byfluorine atoms methyl and phenyl rings: TA-CF3T andTA-PhF5T. These results correspond well with theresults of the microscale measurements. The influence ofthe steric and the electronic character of triazine sub-stituents is different than that observed in the micro-scale. For the chain-containg hybrid composites(TA-CDMT, TA-C8T, TA-CF3T, and TA-FCDMT)the steric effects have no significant influence. However,the electronic character is of fundamental meaningagain. The full rearrangement of (–CH2–)8-H chain(TA-C8T) to (–CF2–)8–F (TA-FCDMT) causes that therelative friction coefficient increases significantly. De-spite the fluorine carbons chain presence, which shouldgive antifriction protective layer, the extremely strongwithdrawing effect in the nanoscale may be responsiblefor the high increase of the relative friction coefficientobserved.

On other hand, when hydrogen atoms in aromaticring are replaced (TA-TPhT) with a fully fluorinatedring, the friction coefficient decreases.

For the hybrids contain aromatic ring (TA-TPhT,TA-BzT, and TA-PhF5T), the steric effect is important,but the character of the substitution of the aromatic ringis of much higher importance, especially when the

O

N N

N

NH

O OO

N N

N

NH

OO

N N

N

NH

O

N N

N

NH NH2NH2

OO

N N

N

NH

OO

N N

N

NH NH2 NH2 NH2NH

OO

N N

N

F

F

F F

F

F

FF

F F

NH2

CA B

O

Figure 8. The general idea of: (a) a long hydro-carbon chain protective coating, presented by the TA-C8T hybrid composite. (b) The steric

compression in the TA-TPhT hybrid composite. (c) The steric compression in the TA-PhF5T hybrid composite.


aromatic ring is fully substituted with electron with-drawing fluorine atoms. Hence, the increase in frictioncoefficient is normally observed in the case of(TA-TPhT, and TA-BzT). The difference betweenTA-TPhT and TA-BzT composites can be explained bythe stiffness of the surface structure. It is known that ifthe thin layer is formed on a surface, it has an almostcompletely ordered character. A less ordered layershould possess better friction properties in the nanoscale[11–13], if only the previously described conditions arerealized (aromatics substituents’ character).

3.4. Comparison of micro and nanoscale results

For comparison purposes, the friction coefficient of agiven sample, measured in the microscale, was calcu-lated as the average over the full range measurements’results, presented in figures 6 and 7. Such a calculationwas justified, because in the full range of the appliedloads, the friction coefficient varied insignificantly. Withthis approach, a similarity between friction results in themicro and nanoscale can be seen. Such correlation wasfound for the group of non-fluorine hybrid composites,as shown in figure 12. It can be said that the friction

Figure 9. AFM topography images (5� 5 lm2) of the starting material and hybrid composites: TA (A), TA-BzT (b), TA-PhF5T (c).

0,000

0,050

0,100

0,150

0,200

0,250

0,300

0,350

TA TA-C8T TA-CDMT

Composite Materials TA-m (Series A)

Rel

ativ

e Fr

ictio

n C

oeffi

cien

t µ

TA-BzT TA-TPhT

Figure 10. The results of the nanofriction tests for non-fluorinated

hybrid composites.

0,000

0,050

0,100

0,150

0,200

0,250

0,300

0,350

TA TA-CF3T TA-FCDMT

Composite Materials TA-m (Series B)

Rel

ativ

e Fr

ictio

n C

oeffi

cien

t µ

TA-PhF5T

Figure 11. The results of the nanofriction tests for non-fluorinated

hybrid composites. Fluorinated hybrid composites.


protection behavior of non-fluorine triazine modifiers issimilar in the micro and nanoscale, despite the differentscale effects, mutual interactions, forces character, etc.The significant difference in the influence of electronwithdrawing substituents (fluorine) did not allow us topresent a convincing proof to point the correlationbetween the micro and nanoscale measurements forfluorine hybrid composites.

4. Conclusions

From the presented work, it can be concluded that thearyloxy- and alkoxy-triazines are good surface modifiers.In most cases, the use of 2-chloro-4,6-dioctyloxy-1,3,5-triazine lead to the formation of the best hybrid com-posite. In the microscale, if the carbon chain is longer(independently of the carbon chain character – fluori-nated or non-fluorinated), a greater decrease in the fric-tion coefficient was observed. The strong influence of thesteric effect resulted in slightly worse properties of thearomatic-containing hybrids, in comparison to the oth-ers. The electron withdrawing substituents, like fluorine,can compensate for this effect, though. The order ofimproving the microfrictional activity, depending on thekind of the triazine ring substitution, is:

n�octyloxy! 1H; 1H�perfluorononyl�1�oxy! methoxy� ¼ 2; 2; 2�trifluoroethoxy! benzyloxy�¼ phenoxy� ¼ pentafluorofenoxy� :

In the nanoscale, the highest reinforcement efficiencywas observed for the non-fluorinated carbon chainsubstituted composites, like silica/aminosilica-dioctyl-oxytriazine (TA-C8T). The character of the substitutionis much more important than the steric effect, if only thearomatic ring is fully substituted, especially by electronwithdrawing substituents.

For the group of non-fluorine hybrid composites, acorrelation was found between friction results in themicro and nanoscale.

Acknowledgments

This work was supported by the State Committee ofScience Grants 4 T09B 071 24 and 4 T07B 03626. Theauthors would also like to thank Prof. Z. Kaminskifrom the Institute of Organic Chemistry at the TechnicalUniversity of Lodz, for help with synthesis of triazinederivatives.

References

[1] G.J. Brinker and G.W. Scherer, Sol-Gel Science. The Physics and

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0,00

0,05

0,10

0,15

0,20

0,25

0,30

0,35

TA TA-CDMT

Composite Materials TA-m

Fric

tion

Coe

ffici

entµ

Microfriction Nanofriction [a.u.]

TA-C8T TA-BzT TA-TPhT

Figure 12. Comparison micro and Nanofriction results for TA-m

composites.


Friction Properties of Triazine Containing Hybrid Composites

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